Plastic hubs are utilized in composite wheel assemblies to produce durable, lightweight, low cost wheels for numerous applications. Such wheels usually include an outer tire of rubber or the like for absorbing shock and imparting skid resistance to the assembly, and an inner bearing of metal or the like for added strength and wear life. Generally two approaches have been taken for incorporating plastic hubs into multipart wheels. One method devised was to separately mold single-piece rigid hubs for later assembly. Separately molded hubs are desirable in that they can be easily and cheaply manufactured at high speeds using various types of plastics. However, the one piece preformed plastic hubs have several disadvantages. First, the hub and tire must be precisely toleranced to permit facile assembly, yet also provide for firm retention of the tire on the hub under full load conditions. Usually the tire is forced fitted over the hub; however, the fact that the tire must be stretched over the hub necessarily limits the ability of the tire and hub to form a secure assembly. Also, it is difficult to incorporate locking structure which will aid in holding the tire on the hub and prevent relative movement therebetween, both along the rotational axis and in the lateral direction.
Another prior art method for producing the composite wheel involves molding the hub in situ between a concentrically positioned tire and bearing. By this method, the hub can be firmly molded around the tire thereby assuring a secure assembly. To further guarantee a durable assembly, intricate interlocking structure may be used, such as lateral projections in the hub extending into corresponding tire grooves, since the fluid plastic will readily fill the space defined between the mold and tire. However, the molding method is unduly expensive in that a great deal of labor time is required to individually place bushings and tires into the mold and insure that they are properly positioned. Also, if any of the parts are improperly positioned, or if the particular molding cycle is faulty in any respect, the entire assembly must be scrapped.
According to the present invention, a composite wheel assembly includes a multipart hub fabricated of a pair of hub members held in abutting relationship by the engagement thereof with a common center core or bushing. The hub members may be formed of a wide range of plastics, including nylon, ABS, and polystyrene. Each of the hub members includes an inner rim portion which is notched at the axial outermost end thereof at circumferentially-spaced intervals therearound in order to facilitate the radial flexure thereof. Further, each of the outermost ends of the inner rim portions includes radially inwardly directed detents thereon. When a common cylindrical center core or bearing member is inserted in an axial outward direction through the hub member pair, the detents on each respective rim portion engage the center core and are flexed radially outwardly. As the center core is inserted further through the inner rim the respective detents snap into and engage with an annular groove formed on the exterior surface of the center core adjacent each end thereof. The relationship of the hub member pair with the annular grooves on the center core is such that when the detents snap into and engage the respective annular groove, the hub members will be positioned in abutting relationship with the mass of the hub equally distributed about the center line of the center core and composite wheel assembly. The constant and uniform pressure created by the bushing by the outward flexing of the inner rim portions helps to maintain the concentricity of the composite wheel assembly and minimizes the possibility that the wheel assembly will become misaligned during use. When assembled, the tire is held centrally between the two hub members by a tire support portion carried by each hub member and the tire is formed to accept laterally extending clincher beads on each of the hub members to further maintain the tire in place on the hub. Anti-rotation lugs on the clincher beads extend through slots in the tire to prevent slippage of the tire about the hub during use.
It is, therefore, the main object of the invention to provide a unique multipart hub assembly which permits the construction of a durable wheel assembly in both a simple and inexpensive manner.